In the earlier series' games Shell would halve magic spells' effectiveness affecting both offensive spells as well as curative spells. In the more recent installments Shell cuts the damage from offensive spells by a third, and does not affect curative spells.

Shell is granted by the Shell spell cast by Rosa and Fusoya. In the GBA and PSP versions, Edward'sSing command changes to Chant while equipped with the Harmony Ring, granting Protect and Shell to the entire party.

Shell is only obtainable through the White Magic spell Shell, the Blue Magic spell Mighty Guard, and the ability Magic Shell. Shell will reduce all magic damage by 50% as well as reducing the hit rate of all non-unblockable magic attacks by half.

The spells MBarrier, Big Guard, and Wall grant MBarrier status to a party member, while the Protect Ring grants MBarrier at the start of the battle. On the barrier gauge to the right, it appears as the lower barrier.

Shell can only be acquired by casting Shell, using a Shell Stone, using Mighty Guard or Wall, or through the auto-ability Auto-Shell. It halves all magical damage and curative spells and lasts for 32 seconds.

The character is enveloped in a magick field, increasing magick resist and reducing magick damage taken. The effect is temporary.

—Description

Shell can be granted by casting the Shell or Shellga spells, or by equipping the Shell Shield. An enemy exclusive ability, Greater Barrier, grants Shell along with Protect. Shell reduces magic damage taken by 33%. It also reduces the success chance of bad status aliments by half, making it useful around undead enemies due to their common use of magick and status effect spells.

In the Japanese version, the icon for the Shell status is a green seashell. This is changed to a green hexagon in the overseas version.

Rank III Esper Tiamat knows the Mighty Guard spell that bestows both Protect and Shell buff on all allies in range. Mighty Guard is the only ability in Final Fantasy XII: Revenant Wings, which lets both Protect and Shell co-exist on a unit.

Shell is achieved via the Synergist spell or shrouds used before battle. Accessories can also grant it automatically. Shell increases resistance to magical damage and healing by 33% and its base duration is 150 seconds, but the overall duration is affected by caster's Synergist level, chain and passive abilities. Shell stats are removed by Dispel, Dispelga and Deshell, and Deshellga. There also exists a stronger variant, called Shellra, that wears off faster but halves magic damage to the user.

Similar to Protect, Shell reduces the caster's magickal power by 1/3 in the formulas, so it not only reduces the power or hit-rate of spells, but also reduces the weapon damage done by a staff or rod because they both apply the wearer's magickal power rather than physical power to calculate the damage amount.

Shell does not affect damage from spells that subtract a certain percentage of the target's HP (such as Demi and Lich), though it does affect the success rate of these spells. Shell lasts for 32 ticks.

In Bravely Default, Shell is not a status. Instead, the spell adds a flat 25% to the current Magic Defense modifier, to a maximum of 150%. This modifier will last for four turns before reverting to normal.